A method of estimating GPS instrumental biases with a convolution algorithm

This paper presents a method of deriving the instrumental differential code biases (DCBs) of GPS satellites and dual frequency receivers. Considering that the total electron content (TEC) varies smoothly over a small area, one ionospheric pierce point (IPP) and four more nearby IPPs were selected to build an equation with a convolution algorithm. In addition, unknown DCB parameters were arranged into a set of equations with GPS observations in a day unit by assuming that DCBs do not vary within a day. Then, the DCBs of satellites and receivers were determined by solving the equation set with the least-squares fitting technique. The performance of this method is examined by applying it to 361?days in 2014 using the observation data from 1311 GPS Earth Observation Network (GEONET) receivers. The result was crosswise-compared with the DCB estimated by the mesh method and the IONEX products from the Center for Orbit Determination in Europe (CODE). The DCB values derived by this method agree with those of the mesh method and the CODE products, with biases of 0.091?ns and 0.321?ns, respectively. The convolution method's accuracy and stability were quite good and showed improvements over the mesh method.     

PVC糊树脂对交联PVC泡沫塑料的影响

通过水煮发泡制备交联聚氯乙烯泡沫塑料,讨论了聚氯乙烯(PVC)糊树脂对泡沫制备过程中经制糊、模压和发泡工艺得到的产物的影响,研究了PVC糊树脂对制备的交联PVC泡沫压缩性能的影响.结果表明:制备交联聚氯乙烯泡沫塑料适宜的糊黏度是4～9 Pa·s;PVC糊树脂的K值较大或水萃取液pH值呈碱性可有效防止模压过程中PVC的降解;PVC糊树脂的水萃取液pH值呈碱性可催化发泡反应,有利于得到低密度泡沫且缩短发泡时间;随着其K值增加,制备的泡沫压缩强度增大,但是K值过大时,制备的泡沫泡孔较大,压缩强度反而降低,适宜的K值为70～80.     

空间环境用耐低温硅橡胶密封材料研究

文章介绍了国内外对耐低温硅橡胶的研究进展,并结合已在空间环境应用的6710耐低温硅橡胶的各项性能和密封试验验证结果,指出耐低温硅橡胶在卫星结构、飞船驱动机构、空间对接、飞船生保系统等空间领域中得到了广泛应用.随着空间站、深空探测等任务对更低温度密封需求的增加,需开展耐更低温度硅橡胶材料的研制及其在空间环境下的演化规律的...     

国外高超声速组合推进技术概述

推进技术是高超声速武器的核心技术,以超燃冲压发动机为基础的高超声速组合推进技术是高超声速武器的首选动力方案。本文介绍了几种以超燃冲压发动机为基础的组合推进方案,并简要介绍了美国、日本以及印度的技术发展现状。     

Simulation analysis for effects of bone loss on acceleration tolerance of human lumbar vertebra

The purpose of the present study was to analyze and predict the changes in acceleration tolerance of human vertebra as a result of bone loss caused by long-term space flight. A human L3–L4 vertebra FEM model was constructed, in which the cancellous bone was separated, and surrounding ligaments were also taken into account. The simulation results demonstrated that bone loss has more of an effect on the acceleration tolerance in x-direction. The results serve to aid in the creation of new acceleration tolerance standards, ensuring astronauts return home safely after long-term space flight. This study shows that more attention should be focused on the bone degradation of crew members and to create new protective designs for space capsules in the future.     

成都空管自动化系统ADS-B处理模块设计与验证

基于ADS-B地面站及成都数据评估试验监测系统的建设需要,本文给出了成都自动化系统ADS-B处理功能的总体设计和系统架构,实现了自动化系统的ADS-B处理功能,并实现了ADS-B模块与自动化系统的隔离并行运行,确保ADS-B处理模块运行不影响自动化系统的保障能力。同时,通过对成都应急自动化系统的ADS-B处理能力和精度进行了飞行校验,结果证明系统各软件模块运行正常,处理结果正确,达到设计要求。